Genetic mechanisms controlling cellular differentiation in a eukaryote, Drosophila, are being analyzed. The gene-enzyme system for alpha-amylase is being developed for this purpose. A selective screen for mutations of control genes which may reglate the expession of the structural gene for amylase, Amy, or its products at various levels from transcripton to the ultimate degradation of the enzyme is being developed. A selective particle to screen for amylase-deficient types is being tested. The starch-diet induced "puffing" in the Amy region of larval midgut polytene chromosomes of D. hydei is being used as a model to study similar phenomena in the small midgut chromosomes of D. melanogaster by means of Scanning EM. If successful, this technique will be incorporated into our selective screen for mutants which affect transcriptional activities at the Amy locus. Transmission EM studies of the midgut are underway to study the intracellular distribution of amylase by means of the immuno-ferritin method. Mutants affecting its synthesis and/or distribution may thus be visualized. The genetic control of midgut activity patterns for amylase, i.e. the distribution of cell synthesizing and secreting amylase, is under analysis. A "temporal gene" which controls amylase patterns in the posterior midgut of adult flies has been genetically defined and named map. Efforts are being made to determine the level at which this gene controls amylase activity. A whole array of midgut activity patterns has been revealed for the adult flies of D. melanogaster and the genetic control of these patterns is under analysis. BIBLIOGRAPHIC REFERENCES: Doane, W.W. 1976 The alpha-amylase system in Drosophila. Workshop on Genetic Regulation in Higher Eukaryotes: Class Notes, pp. 36-37, Salt Lake City, Utah (abstr.), Feb. 12-15, A. Chovnick and K. Paigen, organizers. Doane, W.W. and I. Abraham 1976 Control gene for midgut amylase activity patterns in Drosophila. J. Cell Biol., 70 (2, pt. 2): 266a (abstr.).